Racemic 2-propyloctanoic acid is known as a preventive and treating agent for neurodegenerative diseases caused by dysfunction of astrocytes (cf., for example, WO 99/58513). As a result of studies thereafter, it has been clarified that 2-propyloctanoic acid of an R-form has a particularly strong activity and, therefore, various investigations have been carried out for a process for an efficient production of an R-form substance.
With regard to a process for producing (2R)-2-propyloctanoic acid, (1) a process in which camphor sultam is used as an asymmetric auxiliary group, (2) a process in which L-prolinol is used as an asymmetric auxiliary group, (3) a process in which racemic 2-(2-propynyl)-octanoic acid is reduced after optical resolution (cf EP-A-1078921, JP-A-8-295648 and JP-A-8-291106), etc. are known.
With regard to a synthetic method for an optically active 4-alkanol which is one of the intermediates used for the production of (2R)-2-propyloctanoic acid, a process in which an optically active alkyloxirane is allowed to react with ethyl magnesium halide is disclosed (cf JP-A-1-275541).